When a casting is produced, it is usually the case that a burr or flashing remains about some portion of the raw casting as a result of the joint in the casting mold. It is well-known to remove such burrs or flashings from the raw castings by trimming them with grinding wheels or other cutting tools wherein either the workpiece or the tool is guided by hand so that the tool follows the basic contour of the workpiece and removes only the flashing therefrom.
Because of the fact that this trimming operation requires a great deal of hand labor, attempts have been made to automate the process using such devices as industrial robots. In this technique, a grinding tool is attached to the arm of a robot and is guided along the workpiece by a previously programmed control so that the joint flashing is ground away. The programming of this control is accomplished in a teaching process wherein individual points of the contour of a sample workpiece are approached by the tool and numerical data representing the contour points are stored. The intermediate values required for moving the tool around the workpiece are determined by a computer which forms an integral part of the control system for controlling the movements of the tool. When an apparatus of this type is used, each new workpiece, having a new contour, requires a new "break-in" or instructional process and corresponding storage capacities. Also, slight variations in contours between workpieces, even those which are basically the same workpieces, and also the slight lack of precision in the positioning of the workpieces cannot be detected by a control of this type, and, as a result, a procedure using a machine of this type results in an imperfect removal of the burr or flashing. In addition, such an arrangement requires a considerable capital investment and a further considerable expenditure of time for the "learning" process as a result of which the trimming process, despite the saving of labor costs, is nevertheless quite expensive.
A different type of system, somewhat less relevant, employs a grinding disc controlled by an optical-electric pattern following control in which the grinding head moves in accordance with the movement of an optical device which follows a pattern having a basic contour similar to the workpiece. This kind of machine is used for outside contours of workpieces produced in large quantity such as, for example, crankshafts, camshafts, etc., and likewise has the previously mentioned disadvantages.
Trimming machines with punching attachments with which whole contours or partial contours are trimmed in one operation have also been known. This process is similarly suitable only for workpieces which are produced in large quantity.